It’s natural to blame sleep problems on stress or physical changes that come with age. But many cases of either sleeplessness or poor sleep are caused by a handful of specific problems, most of them fixable with lifestyle changes or the help of a doctor. Here, five little-known causes of sleep problems and what to do about them.

1. Light

How it disrupts sleep: You probably already know that when you stay up late under bright lights, you interrupt your body’s natural sleep-wake cycle, because light tricks your brain into remaining in daylight mode. Less well known is that the light from computer screens and iPads shining directly into your eyes at close range is especially troublesome. Why? Part of the problem is that the light from these devices is at the blue end of the spectrum, which scientists believe is particularly disruptive to circadian rhythms. Blue light, although common during the day, doesn’t occur naturally during the evening.

The evidence: Studies have long shown that shift workers and those who work late at night have poorer sleep and higher incidences of certain conditions associated with lack of sleep than those who regularly sleep eight or nine hours at night. A recent study published in Cancer Causes & Control, for example, found that the countries generating the most light at night have the highest incidence of breast cancer. And studies at the Light Research Center at Thomas Jefferson University in Philadelphia have found that the use of computers, lighted readers, and TVs at close range is tied to a higher incidence of sleeplessness.

Who’s at risk: Everyone exposed to light shortly before bed or during sleep. Light is also bad for hearts, which need deep sleep to recharge. Surprising fact: Every year there’s a spike in the number of heart attacks just after the start of daylight savings time in the spring.

What to do: Dim the lights and turn off all lighted screens at least an hour before bed. If you use a reading light, make sure it’s not any brighter than necessary and doesn’t shine in your eyes. Do a “light police” room check: Are there streetlights outside your windows? Use blackout curtains or shades and make sure they fit the windows tightly so no light seeps in around the edge. Charge laptops, phones, cameras, and other devices in another room. Use an alarm clock without a lighted dial, or turn it to face the wall. Keep a flashlight next to your bed and use it whenever you have to get up to use the bathroom or let the dog out — and be careful to point it away from yourself so you don’t look into the beam. Don’t turn on an overhead light, and never use nightlights. If you must use a laptop, turn down the screen brightness as low as you can tolerate and prop the laptop as far away from you as your typing arms will reach. If you love eReaders, try a Kindle or other device with a screen that’s not backlit.

2. Pain

How it disrupts sleep: Just about any kind of pain signals sent by the brain — jaw pain, headaches, back pain, or arthritis, for example — disrupt sleep, lifting you from the deep, restful REM cycle into lighter sleep or causing you to sleep fitfully and partially wake up over and over, which experts call “microarousals.”

The evidence: Surveys of chronic pain sufferers reveal that between 60 and 90 percent sleep poorly. But many don’t realize that their pain is the cause of their poor sleep. “This can become a vicious cycle,” says Thomas Roth of the Sleep Disorders and Research Center at the Henry Ford Hospital in Detroit, because “even partial sleep disruptions can increase sensitivity to pain.” In other words, even mild pain causes poor sleep, which in turn leads to more pain.

Who’s at risk: Anyone who suffers chronically painful conditions such as arthritis, back or neck pain, jaw alignment problems, dental pain, fibromyalgia, headaches, or any other type of chronic pain.

Note: The pain doesn’t need to be severe; studies show that even mild pain disrupts sleep. According to Roth, frequent microarousals can occur throughout the night without your being aware of them. The result is that you never attain deep REM cycle sleep and wake up feeling tired and grumpy, but you don’t know why.

What to do: Take steps to treat your pain proactively. Using over-the-counter pain relief is a start, but it’s always best to consult with a doctor and develop a comprehensive pain-relief program. For example, you may need physical therapy to combat back and neck pain, or migraine medication if your frequent headaches might be migraines. If bruxism (teeth grinding) or jaw clenching is leading to jaw pain, a mouth guard is often the solution.

3. Disrupted breathing

How it disrupts sleep: When oxygen flow to the brain is interrupted, your brain sends a warning signal that wakes you up either fully or partially, causing fitful sleep or preventing deep, restful sleep. The result: You wake feeling like you didn’t sleep well, even if you were out for nine hours straight.

The best known version of this is apnea, which is a complete stoppage of breathing. A much more common and less recognized problem is upper airway resistance syndrome, or UARS. In UARS, structural blockages somewhere in the airway — nasal congestion, your tongue falling back and blocking the back of the throat, or just having a smaller airway to begin with — begin to interfere with the flow of air. What happens is that you wake up over and over again without knowing it, but the sleep interruptions last only a few seconds, too short to be detected by a standard sleep apnea test.

The evidence: “Even subtle levels of restricted breathing can lead to deep brain stimulation and arousals that prevent your ability to stay in deep sleep,” says otolaryngologist Steven Park, an otolaryngologist and author of Sleep, Interrupted: A Physician Reveals the #1 Reason Why So Many of Us Are Sick and Tired. “You don’t realize you’re waking up, but your brain wakes up, so it’s now in a light sleep. We see people who are waking up 100 times a night.”

Who’s at risk: People who breathe through their mouths or have chronic congestion, such as from asthma or allergies. If you sleep more poorly on your back, this can be a sign of UARS, because when you sleep on your back your tongue is more likely to sink back and block the entrance to your throat. If you have a narrow face, a thin neck, or had extensive orthodontic work to correct a crowded jaw, you’re likely to be at particular risk for UARS, says Park.

What to do: Start with some self-tests. Try using pillows to keep yourself on your side, or put a tennis ball in the back pocket of pajama bottoms, so you can’t sleep on your back. If your nose often feels stuffed up, you might find relief with breathing strips, available at the drugstore. Another option is to try is a device designed to hold the nostrils open; brand names include Nozovent and Breathe with Eez. A saline nasal spray works for many people. If you have congestion due to seasonal allergies, try an antihistamine. (But if you take one that can act as a stimulant, such as Claritin or Sudafed, don’t take it too close to bedtime.)

If none of these help, ask your doctor to refer you to an ear, nose, and throat (ENT) specialist, who can evaluate whether you’re a candidate for Continuous Positive Airway Pressure (CPAP), a nasal mask that delivers air directly through your airways. An ENT can also determine whether tongue position is causing your UARS, in which case a dental device that pushes the jaw and tongue forward can help.

For many people, losing a few pounds can be the ticket to better sleep, since excess weight is linked to all kinds of breathing problems, including UARS, snoring, and sleep apnea.

4. Medications

How they disrupt sleep: Medications sometimes have side effects that trigger sleeplessness or interfere with deep sleep. Most common culprits: asthma medications, corticosteroids, blood pressure medications, and antidepressants.

Also, many ingredients in common medications act as stimulants. They may cause jitteriness during the day and trigger sleeplessness or prevent deep sleep at night. Example: Bronchodilators like albuterol and salmeterol, commonly used to treat asthma, bronchitis, and COPD, can amp you up and interfere with sleep, yet patients are often directed to use them at the end of the day. Other common medications that can interfere with sleep include SSRIs, such as Prozac and Paxil, and beta-blockers taken for high blood pressure and heart disease.

Sometimes medications sabotage your sleep indirectly. Diuretics, for example, can interfere with sleep by causing you to use the bathroom at night. Tagamet (generic name cimetidine), taken to control reflux and ulcers, can cause sleeplessness, especially when combined with caffeine or other medications. Like many side effects, sleeplessness from medications can affect some people but not others; Propecia, used to treat hair loss, and the antihistamine loratadine (brand name Claritin) are both known to cause sleeplessness in a percentage of those who take them. Some people react to opioid pain medications with rebound sleeplessness, feeling sleepy at first but then waking up and being unable to get back to sleep.

The evidence: Although every medication is tested for side effects during the FDA approval process, in many cases evidence of side effects mounts over time as a drug enters more widespread use. Albuterol has been widely reported to cause restlessness, nervousness, and sleeplessness. An article in the European Journal of Clinical Pharmacology also found that beta-blockers interfere with melatonin release.

Recent studies have found that Prozac, Zoloft, Celexa, and other SSRIs affect sleep in a significant number of patients. If you’re using an antidepressant, be sure to talk to your psychiatrist about any possible sleep problems and ask about alternative antidepressants if this is an issue.

Who’s at risk: Those taking regular medication for a chronic condition such as asthma, depression, high blood pressure, or pain. A medication that you take once is less likely to cause an ongoing sleep issue because you take it for a short period of time and are more likely to notice the side effect. When you have a chronic condition, you’re more likely to attribute any sleep problems to the condition rather than the treatment.

What to do: Any time you’re prescribed a new medication, ask the doctor to discuss in detail all side effects you should be alert to. It’s always a good idea to ask both the doctor and the pharmacist, “How will this medication affect my sleep?” Because some medications cause sleepiness, some interfere with sleep, and some do both, asking the question in an open-ended way will get you the most information.

5. Depression

How it disrupts sleep: Fatigue is one of the most prevalent symptoms of depression, yet many people don’t realize how closely related depression and poor sleep can be. Depression wreaks havoc with your natural biological rhythms; many people with depression have trouble getting out of bed in the morning, and they oversleep or get fatigued and nap during the day. Yet their sleep is fitful and of poor quality, so despite spending more hours ostensibly sleeping or trying to sleep, they don’t feel well rested. Then at night, depression sufferers often have trouble maintaining a regular bedtime routine. Having slept late in the morning or napped late in the day, they may not feel sleepy. Anxiety, which often accompanies depression, may cause excessive late-night worry that contributes to sleeplessness.

The evidence: Because the relationship between depression and insomnia is a chicken-and-egg cycle, experts have studied it from both directions. Psychological studies have found that a high proportion of those with depression suffer from either sleeplessness or disrupted sleep, and a recent study by the University of Maryland found that 40 to 60 percent of people with sleeplessness show signs of depression.

Who’s at risk: Those with a history of mood disorders such as depression and anxiety, or anyone who has recently undergone a stressful life event likely to trigger depression.

What to do: One of the most effective steps you can take in this situation is to exercise vigorously during the day. According to experts at the University of Maryland, exercise combats depression by increasing serotonin levels in the brain. It’s also one of the best ways to get your sleep-wake cycle back on track. Do 45 minutes to an hour of physical activity before dinner, and you’ll feel tired earlier and sleep more deeply. If your low mood persists, consult a therapist or ask your doctor for a referral to a psychologist or psychiatrist.